Pay securely with an Android smartphone, completely without Google services: This is the plan being developed by the newly founded industry consortium led by the German Volla Systeme GmbH. It is an open-source alternative to Google Play Integrity. This proprietary interface decides on Android smartphones with Google Play services whether banking, government, or wallet apps are allowed to run on a smartphone.
Read only doesn’t cover what’s needed. You need something that holds a keys that cannot be extracted. Ideally, the institution sends it a challenge, it signs the challenge and returns it. You need the keys not to be retrievable.